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We studied diversity of algae and cyanobacteria in the wetlands of protected natural lakes with salinity ranging from 0.19 up to 32.7 in the arid/semiarid regions of Northern Kazakhstan. In plankton and periphyton of 34 lakes, we found 254 species belonging. to 113 genera of 8 algal divisions. The diversity in arid regions is represented by widespread species of diatoms, green algae, and cyanobacteria in similar proportions. Alkaliphiles, among the indicators of acidification, and betamesosaprobionts. among the indicators of saprobity, predominated. The indices of saprobity in lakes varied from 1.47 to 2.7, reflecting low-trophic and low anthropogenically disturbed wetlands. Oligohalobes-indifferents are most common. Highly diverse algal communities were found irrespective of various levels of mineralization. As a consequence of aridization, salinity increase suppressed algal diversity. The mineralization was the most important variable defining the diversity levels, irrespective of the type and location of wetland lakes in the arid regions.